Unless they are maintaining their whole global index, it IS a Ui over Bing. Don't be fooled by their 400+ sources, that stuff just affects things like the answer box
DDG:
neeva.co, neeva.co/blog, moneycontrol.com, indiatimes.com, nytimes.com, neeva.tech, neevagroup.com, babycenter.com
https://duckduckgo.com/?t=ffab&q=neeva&atb=v63-1&ia=web
Bing:
neeva.co, nytimes.com, androidauthority.com, medium.com, oflox.com, gomoguides.com, neeva.tech, neevagroup.com
https://www.bing.com/search?q=neeva
(I don't use Bing, and DDG isn't supposed to track me, so neither should be personalized results.)
https://i.imgur.com/fML3x0l.png (in French)
Once it is set to my country (France), then I get almost identical results.
I don't know how to deactivate this feature on Bing, so I could not compare Bing and DDG in the case where the "location" setting would be ticked off on both sites.